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Groupe AUREL (AUtomatique des pR0cessus ELecm"ique) Phone number: 83.59.59.59 : Fax number 83.44.07.63 ENSEM -INPL (CNRS URA 821) 2. Avenue de la fcn-&.de Haye. 54516 Vandoeuvre-ks-Nancy. France AbstractThis paper presents a study and an implementation of digital synchronization for the control of a three-phase converter-inverter driving a self-controlled synchronous motor. Begining with a given performance specifications, the study is caried out to look for the solution to various problems encountered in the production of.fuing angle reference in the case of a variable frequency and perturbated network.A completely digital solution is presented. This solution permits us to obtain synchronization and real time clock. These signals are very equirate and valide even in presence of distortions on the network.The two bridge-tensions are filtered by a digital band-pass which is an angle filtering instead of time one.This allows us to keep the same filter coefficients even if the frequency of the tensions changes.In the rectifier part, this angle sampling is obtained in two different manners according to either self-controlled mode or stepby-step mode.In the case of self-controlled synchronous machine, the valves to be fired on the Network Bridge and Machine Bridge are determined from a synchronization system.On the Network Bridge this synchronization system is obtained from the network voltages to which it is connected.On the other hand, for the Machine Bridge things happen in a different manner. In fact, the Self-Controlled Synchronous Machine presents two operating modes : -The Step-by-step mode : corresponding to a starting or very low speed operating phase (Q e QdlO). The induced voltages at the machine level are very low and do not enable a natural commutation. This is therefore being forced : the current flowing into Machine Bridge thyristors is inhibited by setting, during a short time, the Network Bridge in inverter mode.-The Self-Controlled mode : represents the most frequent operation. The induced voltages become sufficient to ensure a natural commutation.To both operations correspond two different synchronization systems for the Machine Bridge : -In the Self-Controlled operation, the synchronizing signals are generated from the induced voltages.

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